The major goal of the core laboratory for the coming year remains the custom synthesis of DNA duplexes of defined sequence for NMR studies of DNA structure and dynamics that are carried out by the various research groups associated with this program project. The core lab will continue to carry out these solid-phase DNA syntheses at the 10 umole level and will provide the preparatively purified oligonucleotides in 20-40 mg quantities as a service to project members. Another major emphasis in the coming year will be preparative production of base-blocked 5'-DMT-protected deoxynucleoside phosphoramidites labelled with deuterium at the 2'-2" position and at the 5'-5" position in the sugar. Our strategy is to prepare the 5' aldehyde by mild pyridinium chromate oxidation of the protected deoxynucleoside followed by sodium borodeuteride reduction of the aldehyde to the 5' alcohol. After analysis by NMR, the base blocked 5'DMT protected 3'-methoxy phosphoramidites will be prepared for subsequent synthesis of site-specific 5'-5" deutero- labelled DNA. For the 2'-2" deutero-labelled deoxynucleosides, we will use Robins' published reductive free-radical deoxygenation of the appropriate ribonucleosides, protected as 3'-5' cyclic tetra- isopropyl disiloxane derivatives, using a trialkyl tin deuteride. The purpose of these materials will be to investigate local motion in the base and in the sugar at various positions in the sequence of DNA duplexes by solid-state deuterium NMR. If time budget permit, we also propose to investigate methods of site-specific 15N labelling of deoxynucleosides for heteronuclear 2DNMR studies of DNA.